A puzzling object just discovered in orbit around
Earth might be an Apollo rocket on a fantastic journey through
the solar system.

Sept.
20, 2002: Something odd is circling our planet. It's small,
perhaps only 60-ft long, and rotates once every minute or so.
Amateur astronomer Bill Yeung first spotted the 16th magnitude
speck of light on Sept. 3rd in the constellation Pisces. He named
it J002E3.

Automated asteroid surveys scan the skies every few weeks,
yet there was no sign of Yeung's object earlier this year. "It
must have entered Earth orbit recently," says Paul Chodas
of NASA's Near-Earth Object Program at JPL. "But it doesn't
match any recently-launched spacecraft."

In other words, it's a mystery.

Above: Andrea Aletti of the Schiaparelli Astronomical
Observatory captured this 10-minute exposure of J002E3 gliding
among the stars of the constellation Taurus on Sept. 17th. J002E3
rotates or tumbles every minute or so, which causes the brightness
variations shown in the picture. [more]

Could it be an alien spaceship? "If it is,"
says Chodas, "the aliens aren't good pilots. J002E3 is in
a chaotic orbit. It loops around Earth once every 48 days or
so, coming as close to our planet as the Moon and ranging as
far away as two lunar distances." There's no evidence that
the speck is moving under its own power. The orbit is constantly
changing because of gravitational perturbations by the Sun and
Moon.

At first Yeung and others thought J002E3 might be a small
asteroid--a reasonable guess. The object is as bright as a 30m-wide
space rock and it's moving about as fast as an asteroid should
move. Mars and Jupiter have captured asteroid moons before; perhaps
Earth had done the same.

It was a good idea, except for the paint.

That's what University of Arizona astronomers found on Sept.
12th when they measured the spectrum of sunlight reflected from
J002E3. "The colors were consistent with ... white titanium
dioxide paint--the type of paint NASA used on Apollo moon rockets
30 years ago," says Carl Hergenrother, who conducted the
study with colleague Robert Whiteley.

Left: Click on the image to view animations
of J002E3's strange orbit. [more]

So, J002E3 might be a spacecraft after all--an old one from
Earth. Where has it been all these years?

"Orbiting the Sun," answers Chodas. "I've traced
the motion of J002E3 backwards in time to find out where it's
been," he explains. Apparently, J002E3 left Earth in 1971,
went around the Sun 30 or so times, and came back again. Chodas,
a expert in planetary motion who has seen plenty of complicated
orbits, says "I've never seen anything like this."

At first glance, J002E3 would seem to be from Apollo 14. That
mission began in January of 1971, and according to Chodas' calculations
J002E3 broke out of Earth orbit in March of the same year. There's
a problem, though: NASA has accounted for all the big pieces
of the Apollo 14 spacecraft. None are missing.

Chodas inventories the mission: On Jan. 31, 1971, a Saturn
V rocket blasted off from Florida with Al Shepard, Ed Mitchell
and Stuart Roosa inside. Two stages of the rocket fell back to
Earth when they exhausted their fuel. A third stage, the S-IVB
fuel tank and rocket engine, which propelled the crew from Earth-orbit
toward the Moon, was likewise discarded. The S-IVB, however,
did not fall back to Earth; it hit the Moon. Ground controllers
guided it there on purpose to provide an impact for lunar seismic
monitoring stations. The lunar module Antares was also
deliberately crashed--more data for the seismic network. The
command module Kitty Hawk returned the crew to Earth.

J002E3 couldn't be any of those things.
"There is an outside chance that it might be one of the
Spacecraft-Lunar
Module Adapter (SLA) panels," adds Chodas, "although
J002E3 appears to be too bright for one of those."

Right: The Apollo 12 Saturn V rocket awaits launch in
1969.

Another possibility is that J002E3 is an S-IVB from Apollo
12. Unlike Apollo 14, Apollo 12's S-IVB did not crash into the
Moon. The crew jettisoned it on Nov. 15, 1969, when it was nearly
out of fuel. Once the astronauts were safely away, ground controllers
ignited the S-IVB's engine. They meant to send the 60-ft-long
tank into a Sun-centered orbit, but something went wrong; the
burn lasted too long. Instead of circling the Sun, the S-IVB
entered a barely-stable orbit around the Earth and Moon "much
like the current orbit of J002E3," notes Chodas.

Eventually, the Apollo 12 S-IVB vanished--no one knows when.
Perhaps gravitational tugs from the Sun and Moon accumulated
until they nudged the engine away from Earth in 1971. In this
scenario, it would have circled the Sun for 31 years until it
was re-captured by Earth's gravity in 2002.

"It's plausible," says Chodas, "but still speculative."

Whatever J002E3 is, it's taking a fantastic journey through
the solar system--and it's not done yet. Chodas' calculations
indicate that J002E3 will leave Earth again in June 2003 to resume
its orbit around the Sun. "Thirty years from now,"
he notes, "it might come back again."

Below: Attached to the Saturn IV-B stage, the Lunar
Module Adapter's four panels are retracted to the fully open
position. This picture was taken during the Apollo 7 mission.
[more]

If
it does, perhaps it will be greeted by human explorers on regular
"milk runs" between the Earth and Moon. They might
detour briefly and discover, once and for all, what J002E3 really
is: a historical attraction, maybe, or something wholly unexpected....

For now the best we can do is watch J002E3 from afar--an unresolved
speck of light easily detected by 8" to 10" telescopes
with CCD cameras. This week J002E3 is gliding through the constellation
Taurus. Where will it go next? Find out by visiting JPL's Near-Earth
Object Program web site, which offers a helpful ephemeris
for observers. J002E3 won't be here long, so catch it while
you can!

Editor's note #2: Could the Hubble Space Telescope take
a picture of J002E3 and see what it is? No. With its 2.4 meter
diameter mirror, the smallest object that the Hubble can resolve
at the Moon's distance is about 80 meters across. J002E3 is no
larger than about 30 meters if it is an asteroid or 20 meters
if it is an S-IVB--too small for Hubble.

Editor's note #1: Earlier this week, Chodas noted
that J002E3 might hit the Moon in 2003. The odds he estimated
were 20%--a figure which was widely reported. The odds have since
declined. His latest calculations indicate that J002E3 has less
than a 1% chance of hitting the Moon before June 2003, and no
chance of hitting Earth. Even if J002E3 did hit Earth, notes
Chodas, it wouldn't reach our planet's surface. "The object
would completely disintegrate in the atmosphere as a beautiful
fireball." Regarding the possibility of a lunar impact,
University of Arizona professor Jay Melosh explains that J002E3
is not traveling fast enough to create a bright fireball if it
hits the lunar surface. "More likely," he says, "the
impact would produce a glowing infra-red cloud like the one astronomers
observed when the Japanese Hiten spacecraft hit the Moon in 1993."

How does J002E3 jump back
and forth between a Sun-centered orbit and an Earth-centered
orbit? "It moves
through the L1-point,"
explains Chodas. Also known as "the 1st Lagrangian
point," the L1 point is a
location in space 1.5 million km closer to the Sun than Earth.
Objects placed there in a circular orbit will move around the
Sun in exactly one year--always directly between our planet and
the Sun. The Solar and
Heliospheric Observatory, for example, is a spacecraft that
lives at the L1 point. It enjoys a continuous view of the Sun,
24 hours a day, 365 days per year. Objects closer to Earth than
the L1 point are controlled by Earth's gravity. Objects beyond
the L1 point are controlled by the Sun. "When J002E3 came
close to the L1 point in April 2002, the object passed throuhgh
L1--like a portal--from a Sun-orbit to an Earth-orbit. At some
time in the future it might leave Earth-orbit in the same way,
back out through the L1 point."